The present invention relates to methods of treating a subterranean formation with stress-activated resins.
Various methods are known for fracturing a subterranean formation to enhance the production of fluids. In a hydraulic fracturing operation, a pressurized fracturing fluid can be used to hydraulically create and propagate a fracture within the formation. Fracturing fluids can also carry and deposit solids, such as proppants particulates, into the fracture. Inside the fracture, the proppant particulates can form a tightly packed permeable mass (sometimes referred to as a “proppant pack”). The proppant pack serves as a physical barrier that prevents the fracture from fully closing and as a conduit through which production fluids can flow. The degree of success of a fracturing operation depends, at least in part, upon the fracture conductivity once the fracturing operation is stopped and production is begun. The conductivity of these proppant packs are somewhat limited because of the relatively small interconnected interstitial spaces between the packed proppant.
In order to ensure that a well-formed, porous proppant pack is created within a fracture, resins are often pre-coated onto the proppant particulates or included in fracturing treatment fluids to coat the proppant particulates downhole. Ideally, the resin is generally capable of preventing proppant particulate migration out of the formation and thus promotes the consolidation of proppant particulates to one another to form a proppant pack. The resin may act to improve the clustering capacity, tensile strength, and flowback control ability of the proppant pack. Resins may additionally promote homogeneous distribution of the proppant particulates within the proppant pack by reducing or preventing any tendency of them to flow out of the proppant pack within the fracture in the subterranean formation. Resins may be particularly useful if the proppant particulates used in a particular fracturing operation have a low density or specific gravity.
Traditional resins are “activated” (e.g., destabilized, coalesced and/or reacted) to transform into a sticky or tackifying compound by temperature alone. As used herein, the term “tacky,” in all of its forms, generally refers to a substance having a nature such that it is somewhat sticky to the touch. Traditional resins are activated by a complex system of several chemicals, some of which are highly toxic, which must be used onsite during fracturing operations. Activation requires intergrain contact of proppant particulates, as well as a sufficiently high subterranean formation temperature. As such, activation may occur in undesirable portions of a subterranean formation (e.g., outside of a fracture) or not at all, resulting in either the absence of a formed proppant pack or an inefficient proppant pack. Moreover, traditional resins flow freely between proppant particulate grains and often result in a dumbbell or other undesirable shape when set up on the proppant particulates that further reduces the interstitial spaces within a proppant pack. Therefore, a single-step resin system that is not temperature dependent and capable of setting up on proppant particulates in desired portions of a subterranean formation (e.g., in a fracture) to produce a porous proppant pack may be desirable to one of ordinary skill in the art.